Even among doctors who said they voted for Trump, only 38 percent said they wanted the act eliminated in its entirety.

Mr. Trump has promised to replace Obamacare with something better. Neither he nor Congress have released specifics.

That might garner support from the physicians surveyed, depending on the provisions of a new plan; 74 percent favored making improvements to Obamacare. But some improvements they want may not be popular with opponents of the law.

For example, more than 66 percent of the respondents said the government should create a public option similar to Medicare to compete with private insurance. Many opponents want the government out of the healthcare business altogether.

More than half (59 percent) of the physicians surveyed supported tax credits that would allow the purchase of private insurance by people eligible for Medicaid, the federally-financed but state-run health insurance program for the poor.

In contrast, only 29 percent supported increasing the use of high-deductible health plans, a proposal being floated around to keep down government costs, and fewer than half of the physicians (43 percent) said Medicare should be expanded to cover people aged 55 to 64.

Some Republican proposals have called for deregulating the private insurance industry, a move that would allow companies to sell health plans across state lines. Only 42 percent of physicians supported that idea.

The primary care physicians were almost evenly split on the idea of requiring all states to expand Medicaid under the auspices of Obamacare, a controversial concept. Many states with Republican governors have refused to do so.

But the provisions of the law that are most popular with the public are very popular with the first-line physicians as well.

Just over 95 percent said it was somewhat or very important to prohibit insurance companies from denying coverage or charging more for people with preexisting conditions, which companies were allowed to do before Obamacare.

Support levels among the physicians were nearly 88 percent for allowing children up to age 26 to be covered on their parents' insurance plan, 91 percent for providing tax credits to small businesses and 73 percent for expanding Medicaid for the poor.

"I do think it's striking that even among doctors who said they voted for Donald Trump for president, only about a third - 38 percent - supported repealing the ACA in its entirety," study coauthor Dr. Craig Pollack, an associate professor of general internal medicine at Johns Hopkins School of Medicine in Baltimore, told Reuters Health.

Only 32 percent of doctors who said they were Republicans favored complete repeal. The rate among Democrats was zero.

The survey was done by mail in December and January. The response rate was 45 percent.

It focused on primary care physicians, a group that includes family practitioners, pediatricians and internal medicine specialists because "they're on the front line trying to advocate for their patients," Pollack said.

In contrast, a survey done by The Kaiser Family Foundation and the Commonwealth Fund during the first quarter of 2015, a year and a half after the botched rollout of the Obamacare enrollment website, found that 52 percent of primary care physicians had an unfavorable view of the law while 48 percent viewed Obamacare favorably.

Political debate over the subject of physician support has been the subject of a lot of hype. For example, in 2012, Republican lawmakers were claiming that 83 percent of doctors were considering leaving the profession because of Obamacare. That claim was based on a survey by a group founded to oppose the law.

PolitiFact, the fact-checking website, ruled the claim false because the survey never directly asked doctors if Obamacare had sparked thoughts of quitting medicine.

A survey of doctors shows overwhelming opposition to the effort by President Donald Trump and the Republican Congress to repeal the Affordable Care Act (ACA), also known as Obamacare. The results, published in the New England Journal of Medicine, show only 15 percent of 426...